2004 Pontiac Grand Prix Clicking noise

Hello. Since I bought the car 3 years ago, it has made a click, click noise when I first start the car for the day. When I drive for 5 minutes, the click, click stops. Only it clicks twice in a row, then about a minute later, it clicks again. Once I get to work, my car sits there for 8 hours. The clicking noise starts all over for about 5 minutes again and then stops. It sounds like it is coming from the exhaust almost. It isn't too loud, but I do hear it. I looked up any recalls or anything for that, but couldn't find anything. What are your thoughts on why it would do that? Thank you for your time.